1. Field of the Invention
The present invention relates to an exchange making terminal apparatuses communicate with one another, said terminal apparatuses being connected to a packet network such as the Internet, an intranet of a private LAN and the like, and connected to a public circuit switching network.
2. Description of the Related Art
The most apparatuses used in a present public telephone network are analog telephones. And an exchange (PBX: private branch exchange) connected to a public telephone network has many special functions so as to provide various services by connecting an analog telephone directly to the PBX as an extension telephone.
On the other hand, voice communication using the Internet (Voice over Internet Protocol: VoIP) can be performed by connecting a public telephone network and the Internet to each other through an exchange (see Patent literature 1: Japanese Patent Laid-Open Publication No.Hei 11-191,791 (FIG. 1), for example).
Also in such a situation, however, it is necessary to accommodate a public telephone network, an extension telephone, the Internet, a terminal 61 adapted to ITU-T Recommendation H.323 (hereinafter, referred to as an IP telephone) and the like, and perform a process of address-converting a called telephone number into a number on a packet network, a calling process, a call connection process and the like also in a packet switching network such as the Internet, and it is necessary also to apply an SS7 signaling signal to a packet switching network (in a conventional public telephone network, a call is transmitted by an SS7 signaling (hereinafter, referred to as No.7) signal until an end office takes part in the call and is managed by each end office).
And there has been needed an exchange capable of being inexpensively adapted to also the case of building a system of only digital data communication using a packet network such as the Internet.